Method And System For Internal Permeate Processing In Reverse Osmosis Membranes

Abstract

A reverse osmosis system includes a multi-element membrane array having a plurality of membrane elements disposed in series and a plurality of permeate pipes receiving permeate from a respective one of the plurality of membrane elements. Each of the plurality of elements has an inlet and an outlet. A plurality of connectors coupling successive permeate pipes together. Each of the plurality of connectors includes one of a plurality of flow restrictors. Each of the plurality of flow restrictors is sized to further restrict permeate flow into a subsequent permeate pipe of the plurality of permeate pipes.

Claims

1. A reverse osmosis system comprising: a multi-element membrane array having a plurality of membrane elements disposed in series; a plurality of permeate pipes receiving permeate from a respective one of the plurality of membrane elements, each of the plurality of elements having an inlet and an outlet; and a plurality of connectors coupling successive permeate pipes together, each of the plurality of connectors comprising one of a plurality of flow restrictors, each of the plurality of flow restrictors sized to further restrict permeate flow into a subsequent permeate pipe of the plurality of permeate pipes.

2. The reverse osmosis system as recited in claim 1 wherein each connector has an effective internal diameter such that subsequent connectors comprises larger effective internal diameters.

3. The reverse osmosis system as recited in claim 1 wherein the plurality of flow restrictors cause net driving pressures of subsequent membranes to increase over the multi-element array.

4. The reverse osmosis system as recited in claim 1 wherein the plurality of flow restrictors cause subsequent membranes to produce substantially the same permeate over the multi-element membrane array.

5. The reverse osmosis system as recited in claim 1 wherein the flow restrictors comprise an orifice having an orifice diameter, wherein subsequent orifice comprise a larger diameter.

6. The reverse osmosis system as recited in claim 5 wherein each connector comprises a body having a connector inner wall defining longitudinal passage therethrough, said body comprising an outer wall, said orifice is disposed in an orifice plug coupled within the longitudinal passage, said orifice plug separate from the body.

7. The reverse osmosis system as recited in claim 6 wherein the orifice plug is fixed within the passage with a first snap ring and a second snap ring, said first snap ring and second snap ring coupled between the passage and an orifice plug outer wall.

8. The reverse osmosis system as recited in claim 6 wherein the connector inner wall comprises first threads in the longitudinal passage and wherein the orifice plug comprises second thread engaging the first threads.

9. The reverse osmosis system as recited in claim 8 wherein the orifice plug comprises an axial slot and a circumferential groove sized to receive an insertion tool.

10. The reverse osmosis system as recited in claim 9 wherein the insertion tool comprises tabs sized to be received within the axial slot and the circumferential groove.

11. The reverse osmosis system as recited in claim 6 wherein each connector of the plurality of connectors comprises a connector outer wall that comprises a shoulder extending inward therefrom, said shoulders defining a shoulder diameter.

12. The reverse osmosis system as recited in claim 11 wherein the orifice plug engages the shoulder.

13. The reverse osmosis system as recited in claim 12 wherein shoulders in subsequent connectors of the plurality of connectors have successively larger opening diameters.

14. The reverse osmosis system as recited in claim 12 wherein an outer wall of the orifice plug comprises a first outer wall portion comprising a first outer wall diameter, said first outer wall portion engaging the shoulder, and a second outer wall portion having a second wall outer diameter greater than the shoulder diameter.

15. The reverse osmosis system as recited in claim 5 wherein the orifice diameter of a first orifice plug is larger than an outer diameter of subsequent orifice plugs.

16. The reverse osmosis system as recited in claim 6 wherein the orifice plug comprises a carrier body have a passage therethrough, said carrier body comprising an orifice plate, an orifice through the orifice plate and a spring disposed within the carrier body, said carrier body comprising an elongated flow restrictor.

17. The reverse osmosis system as recited in claim 16 wherein fluid pressure forces the orifice plate toward the flow restrictor.

18. The reverse osmosis system as recited in claim 17 wherein the flow restrictor it at least partially received within the orifice.

19. The reverse osmosis system as recited in claim 17 wherein the connector inner wall comprises a first inner diameter and a second inner diameter, said carrier body engaging a wall between the first inner diameter and the second inner diameter.

20. A method of operating series connected membranes comprising: providing connectors between adjacent permeate pipes of adjacent membranes having one of a plurality of flow restrictors, each of the plurality of flow restrictors sized to further restrict permeate flow into a subsequent permeate pipe. reducing pressure with each of the flow restrictors; and reducing permeate pressure at subsequent membranes to maintain a substantially equal net driving pressure at subsequent membranes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1A is a schematic view of a prior art reverse osmosis system.

[0022] FIG. 1B is a perspective view of a permeate membrane showing the layers therein of the prior art.

[0023] FIG. 1C is a representative view of a membrane channel generating permeate.

[0024] FIG. 1D is a chart illustrating feed pressure, osmotic pressure, the feed total dissolved solids (TDS), the permeate flow rate and net driving pressure (NDP).

[0025] FIG. 1E is a cutaway view of a pressure vessel having a plurality of membrane elements of the prior art.

[0026] FIG. 2A is a block diagrammatic view of a multistage multi -element pressure vessel configuration of the prior art.

[0027] FIG. 2B is a schematic view of a multi-element pressure vessel according to the prior art.

[0028] FIG. 3 is a cross-sectional view of a first example of a connector used for flow restriction.

[0029] FIG. 4 is a cross-section of a multi-element array having a plurality of connectors such as that of FIG. 3.

[0030] FIG. 5 is a second example of a connector according to the present disclosure.

[0031] FIG. 6 is a chart illustrating the output of a membrane array having a plurality of connectors formed according to FIG. 3 or 5.

[0032] FIG. 7A is a cross-sectional view of a third example of a connector.

[0033] FIG. 7B is a cross-sectional view of the connector of FIG. 7A.

[0034] FIG. 7C is a cutaway view of the connector of FIG. 7A.

[0035] FIGS. 8A and 8B are front and side views of a rod used for inserting and removing the connector of FIG. 7A-7C.

[0036] FIGS. 9A and 9B are a fourth example of a connector of the present disclosure.

[0037] FIG. 10 is a cross-sectional view of a fifth example of a connector.

[0038] FIG. 11 is a chart illustrating orifice size for a fixed orifice or the active orifice of FIG. 10.

[0039] FIG. 12 is a flowchart of a method of operating the connector of FIG. 10.

DETAILED DESCRIPTION

[0040] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. The word subsequent is used to denote downstream or later in the flow path. That is, subsequent connectors are connectors after or downstream from a particular connector.

[0041] The present system is illustrated to a single pressure vessel. However, the following examples may be included in systems with multiple pressure vessels such as those set forth in the description of FIG. 2A and FIG. 2B.

[0042] Referring now to FIG. 3, the present disclosure provides the connector 310A as a replacement for the connectors 66A-66D illustrated in FIG. 1E set forth above. The connector 310A has a connector body 312 formed by a connector wall 318 that has an external diameter D.sub.1. To prevent fluid loss between the permeate pipe and the connector body 312, one or more seals 314 such as O -rings may be incorporated into an external channel 316 on the outside of the connector body 312.

[0043] The connectors 310A are used to connect successive permeate collection tubes 46A-46E together as set forth in FIG. 4 below. Each of the connectors has a flow restrictor 320 that allows each element in the pressure vessel to operate at an optimal flux rate by individual control of the permeate pressure in each element. The NDP for each element should be the same to achieve an approximately equal permeate production form every element. This is done by having very high permeate pressure in the first element to compensate for the low osmotic pressure and then have progressively lower permeate pressure in the following elements to compensate for increasing osmotic pressure. The orifice diameter increases for each element downstream in the housing to reduce permeate pressure. The pressure distribution is therefore exactly opposite to that of a conventional array of membranes. The flow restrictor 320A has an effective diameter D.sub.2 which is less than the diameter D.sub.3 of the connector passage 322. The connector wall 318 has a thicker portion that extends inward to form the orifice 324 the effective diameter D.sub.2 is the area that the fluid flows through to create the desired pressure drop. The orifice diameter of the effective diameter D.sub.2 increases in each subsequent connector. In this example the flow restrictor 320A comprises an orifice 324 that has the reduced diameter D.sub.2 compared to that of the connector passage 322. The orifice 324 creates a pressure drop in the permeate that flows therethrough. Pressure upstream of the orifice 324 is higher than the pressure downstream of the orifice 324. The suitable diameter D.sub.2 for the orifice 324 may be experimentally determined so that the permeate for production for each element is the same.

[0044] Referring now to FIG. 4, the connectors 310A-310D may be inserted into permeate pipes disposed between successive elements 40A-40E of a five element pressure vessel 24. In this example, the same reference numerals are used for the same components illustrated in FIG. 1E with the absence of the valve 72 being removed.

[0045] The orifice 324 is relatively small and thus a great deal of flow resistance is used to raise the permeate pressure in the elements which in turn reduces the net driving pressure which reduces the rate of permeate production. The connector 310B has an increased orifice size or an increased effective diameter D.sub.2 from that of connector 310A. The connector 310B accommodates the permeate flow from the elements 340A and 340B. To allow a desired permeate flow resistance so that the NDP is optimal. The orifice 324 in the connector 310C has a larger orifice size or diameter D.sub.2 than both the previous connectors 310A and 310B to accommodate the preceding flow from out of the membrane elements 40A, 40B and 40C. The diameter D.sub.2 of connector 310C is thus greater than the diameter of the orifices in 310A and 310B. The orifice 324 within the connector 310D also must accommodate the permeate flow from the membrane elements 340A, 340B, 340C and 340D. Thus, the diameter D.sub.2 is also greater than all of the previous orifice diameters from the connectors 310A-310C. To state it in another way each successive effective diameters D.sub.2 in subsequent connectors increases.

[0046] Referring now to FIG. 5, a second example of a connector 310A is set forth. The connector 310A in this example the diameter of the passage 322 is consistent all the way through the housing. That is, the connector wall 318 has a uniform thickness which is defined by the diameter D.sub.3 of the connector body 312. In the example set forth in FIG. 3, the orifice 324 has a fixed diameter D.sub.2 for each of the connector bodies. The diameter D.sub.2 increases in successive (or downstream) connectors. In this example a common connector 310A may be set forth while an interchangeable orifice plug 510 is used to change the effective diameter D.sub.2 of the orifice 324. That is, for each of the successive connectors only the orifice plug 510 may be required to be changed to implement the different sizes. Therefore, the connectors themselves do not have to be replaced, only the orifice plugs 510.

[0047] The orifice plugs 510 may be held in place by a pair of snap rings 512A and 512B. The snap rings 512A and 512B may be received within respective axial slots 514A and 514B formed within the passage 322. That is, the axial slots 514A and 514B may be formed within an inner wall 516 of the connector body 312A.

[0048] The outer diameter of the orifice plug 310 corresponds substantially to the outer diameter D.sub.3 of the inner wall 516. Of course, seals (not illustrated for convenience) similar to those of the seals of 314 may be used to seal the orifice plug 510 to the inner surface 516 of the connector wall 318. However, the snap rings 512A, 5128 may also act as a seal.

[0049] In operation, the first snap ring 512A is inserted within the axial slot 514A. Then, the orifice plug 510 is axially placed within the connector passage 322. The second snap ring 512B is placed within the axial slot 514B to secure the orifice plug 510 into position. Each subsequent orifice plug 510 in a system may be increased in the inner diameter D.sub.2 in the downstream direction. That is, each subsequent orifice plug 510 may have a greater orifice diameter in the downstream direction.

[0050] Referring now to FIG. 6, a plot of the various pressures for a five element membrane array such as that set forth in FIG. 4 is illustrated. In this example, each element has a lower permeate pressure than the preceding element to compensate for the increasing osmotic pressure. The result is that the net driving pressure remains relatively constant through the length of the membrane array. Thus, the permeate flux rate and thus the permeate production for each of the elements is relatively or substantially uniform.

[0051] Referring now to FIGS. 7A-7C, a connector 310A is set forth. In this example the connector 310A includes the connector body 312 having a connector wall 318. The connector passage 322 includes an orifice plug 510 inserted therein. In this example threads are used to secure the orifice plug 510 to the connector wall 318. The orifice plug 510 is a flow restrictor. That is, the connector wall 318 has threads 710 that engage threads 712 on the orifice plug 510. As is best shown in FIG. 7B, the orifice plug 510 has threads 712 while the connector wall 318 has threads 710.

[0052] The orifice 324 has an inner diameter D.sub.2 that changes upon the position of the connector within the membrane array as described above.

[0053] Referring now specifically to FIGS. 7B and 7C, the threaded orifice plug 510 is illustrated having axial slots 714 which may be provided on both ends of the orifice plug 510. The axial slots 714 and the circumferential grooves 716 are formed on the inner surface of the orifice plug 510. This allows the threads 710 on the connector wall to engage the threads 712 on the orifice plug.

[0054] The threads 710, 712, when engaged, are used to hold the orifice plug 510 in place. The threads 710, 712 therefore do not have to be locked or otherwise retained, although thread sealant may be used. The fluid pressure flowing through the orifice plug 510 may be used to retain the orifice plug 510 in place.

[0055] Referring now to FIGS. 8A and 8B, an insertion tool 810 is illustrated having a rod 812 that has tabs 814 extending therefrom. The tab 814 extends a greater diameter from the surface of the rod 812. In this example two tabs 814 are formed at opposite ends of the cylindrical rod surface 813. The tabs 814 are linearly disposed across the center point 816 of the rod 812. The rod 812 has a diameter D.sub.5 that is sized to be received within the passage 718 that defines the orifice 324. The tabs 814 extend a distance that corresponds to the depths of the axial slots 714 and the circumferential groove 716. The rod 812 is long enough to reach into the connector passage 322 so that the orifice plug 510 may be inserted and removed.

[0056] In operation, the rod 812 is aligned so that the tabs 814 correspond to the axial slots 714. The tabs 814 are inserted into the axial slots 714 in an axial direction until they meet the circumferential grooves 716. The rod 812 is then rotated so that the tabs 814 engage and walls 716A or 716B of the circumferential groove 716. The rod 812 is rotated so that the interchangeable orifice plug 510 is also rotated so that ultimately moved in an axial direction into the connector passage 322.

[0057] Referring now to FIGS. 9A and 9B, two connectors 310A and 310B are illustrated. In this example, the connectors 310A and 310B have a connector body 312 that have connector wall 318. The connector walls 318 include shoulders 910A and 910B that extend in an axial direction inward from the wall 318. The space left between the shoulders is a diameter D.sub.6A and D.sub.6B. The diameter D.sub.6A is greater than the D.sub.6B to allow the orifice plug 914 to pass therethrough. The orifice plugs 912 and 914 have first portions 911A, 911B having respective maximum outer diameter D.sub.10 and D.sub.11. Each of the orifice plugs 912 and 914 have a seat 916 and 918 that rest against the shoulders 910A and 910B respectively. The second diameter portions or seats 916 and 918 have a smaller diameter than the diameter D.sub.10 and D.sub.11. Walls 915, 917 extend in an axial direction and connect the first portions 911A, 911B to seats 916, 918. It should also be noted that the shoulders may engage threads disposed on the seats 916 and 918 in a similar manner to that described above with respect FIGS. 7A-7C. That is, threads on the seats 916, 918 may engage threads on the shoulders 910A, 910B. The rod 812 with tabs 814 (of FIGS. 8A, 8B) that engage axial slots 714 and circumferential grooves 716 may also be provided in the orifice plugs 912 and 914. The difference in the diameters of the orifice plugs 912 and 914 are such that the diameter D.sub.11is the maximum diameter on the orifice plug 914 and thus the diameter D.sub.6A is greater than the diameter D.sub.11 that the diameter D.sub.11 of the plug 914 can pass through the shoulders. Subsequent or downstream connectors are designed in a similar manner. This allows the connectors to be removed with rods of various lengths and diameters from all of the connectors between the membrane housings. Over time and over different conditions different size orifices 920 and 922 may be provided. Thus, the outer diameters of successive plugs continue to decrease while the inner diameters of the orifices 920 and 922 continue to increase downstream. Again, the fluid pressure through the orifices 920 and 922 which causes pressure against the orifice plugs 912 and 914 allow the orifice plugs to maintain their position. Different size diameter rods are used to remove the different connector plugs. That is, each rod has a corresponding diameter and thus the tab diameter also is changed.

[0058] Referring now to FIG. 10, a connector 310A.sup.iv is set forth. In this example the seals 314.sup.iv may be used in a similar manner as the seals described above. In this example an active orifice plug 1010 is seated against shoulder 1012. The shoulder 1012 is formed by a diameter 1014 which is less than the diameter 1016. An axial groove 1018 receives a snap ring 1020 for holding the active orifice plug 1010 against the shoulder 1012.

[0059] The active orifice plug 1010 has a housing 1022 which, in this example is three-sided. The active orifice plug 1010 is a flow restrictor. A partial fourth side 1023 may be used to retain components within the housing 1022. The housing 1022 receives a spring 1024 that axially compresses relative to the axial passage through the connector 310A.sup.iv. The active orifice plug 1010 also includes a port 1026. The housing 1022 has an elongated flow restrictor 1028 coupled thereto. The flow restrictor 1028 may have angled portions 1030 that reduce the overall diameter of the flow restrictor toward the inlet 1032 of the housing 1022 the outlet of the housing 1022 is the port 1026.

[0060] The spring 1024 rests against an orifice plate 1034. The orifice plate 1034 has an orifice 1036 therethrough. Fluid flows through the housing 1022 through orifice 1036 and port 1026. The orifice plate 1034 moves in an axial direction relative to the flow and thus reacts to the differential pressure across the connector 310.sup.iv. When the pressure is high enough the spring 1024 compresses in an axial direction as forced by the orifice plate 1034. A higher pressure of the fluid received in the connector 310.sup.iv causes more deflection in the orifice plate 1034. However, the angled portions 1030 of the flow restrictor 1028 restrict the flow variably through the orifice 1036 depending on the orifice plate position. Flow resistance thus increases through the active orifice plug 1010. This further limits the increase in flow. Conversely, if the flow rate decreases the spring 1024 pushes the orifice plate 1034 toward the inlet 1032 (left in the figure) of the connector 310.sup.iv and thus the flow through the orifice 1036 and the port 1026 increases. Changes in pressure yield a smaller permeate flow variation with the flow control orifice versus a fixed orifice such as those set forth in the previous example.

[0061] Referring now to FIG. 11, a chart illustrating the flow difference in flow versus a change in pressure (AP) characteristics of a fixed orifice plate and a flow control adjustable orifice plate is set forth. The change in pressure versus flow is set forth in the diagram of FIG. 11. Deviations in the change in pressure yields a smaller permeate flow variation with the flow control orifice versus a fixed orifice thus keeping the permeate production closer to the optimal value regardless of the feed conditions.

[0062] Referring now to FIG. 12, a method of operating a multi -membrane permeate system is set forth. In this example permeate is generated at a first membrane in step 1212. In step 1212 permeate is communicated into a permeate pipe associated with a first membrane. In step 1214 the permeate from the first permeate pipe is communicated toward the second permeate pipe associated with a second membrane and to a first connector. In step 1216 the permeate is communicated from the first pipe against an orifice plate. In step 1218 the orifice plate is axially moved based upon the pressure of the permeate within the first permeate pipe. In step 1220, the flow is restricted by moving the orifice plate away from the flow restrictor. That is, in step 1220 the flow pressure is less than the spring force and thus the orifice plate is moved away from the restrictor to widen the amount of space available between the orifice and the flow restrictor. In step 1222 the orifice plate is pushed by the pressure of the fluid from the first permeate pipe. That is, the permeate flow is restricted through the orifice plate using the flow restrictor. As mentioned above, when the pressure of the permeate is sufficient to move the orifice plate toward the flow restrictor the flow restrictor and the angled portions at the end of the flow restrictor restrict the flow through the orifice of the orifice plate. As more pressure is provided from the permeate more of the flow restrictor enters the orifice and the flow through the active orifice plug is reduced.

[0063] Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.